字符和ASCII 编码的转换

Char(int)  将ASCII code转换为一个字符， Converts an int ASCII code to a character.

ASCII(char) 将一个字符转换为ASCII code，Returns the ASCII code value of the leftmost character of a character expression.

--convert int to char
declare @char_int binary(1)
set @char_int=ASCII(‘a‘)
select @char_int

--convert int to char
declare @int_char binary(10)
set @int_char=97
select char(@int_char)

参考doc：

CHAR (Transact-SQL)

ASCII (Transact-SQL)